The present invention relates to a product which is externally alloyed with Zr, whether plated or entirely made of the alloy, the method for its manufacture and its use in the most often fashioned or assembled form in a nuclear water reactor.
The two principal zirconium alloys used in nuclear water reactors are zircaloy 2, which contains 1.2 to 1.7% tin, 0.07 to 0.2% iron, 0.05 to 0.15% chromium and 0.03 to 0.08% nickel, and zircaloy 4, which contains 1.2 to 1.7% tin, 0.18 to 0.24% iron and 0.07 to 0.13% chromium, with a maximum content of nickel of 0.007%. These alloys are used for fuel sheathing tubes and for making structural assembly components, and their compositions are set forth in the ASTM B 352 specifications, under the respective designations "R 60802" and "R 60804."
In boiling water reactors, where corrosion is either uniform or of the nodular type, zircaloy 2 is usually used; however zircaloy 4 has been used for the housings and spacers. In pressurized water reactors, where the corrosion is generally uniform, zircaloy 4 is usually used.
Resistance to nodular corrosion is estimated by measurement of the weight gain after testing for 24 hours at 500.degree. C. in steam; resistance to uniform corrosion is estimated by measurement of the weight gain after testing at 400.degree. in pressurized water for 14 days. For corrosion in water and in steam (boiling water), both good resistance to uniform corrosion and good resistance to nodular corrosion are required, as well as a very low rate of hydrogen absorption.
Zircaloy 2 and zircaloy 4 do not act in the same manner with regard to the two forms of corrosion and to hydrogen absorption, and it is difficult to have transformation conditions enabling the use of each alloy with good results in both types of reactors.
Applicant has sought to perfect a product which is more adaptable to these two types of reactors and corrosions.